Resetting current trip mechanism



Feb. 20, 1951 J. G. M. VlTl ETAL RESETTING CURRENT TRIP MECHANISM Filed Jan. 10, 1948 Inventors John G. M. Viti, John l... Lappm,'

Their- Attorney Patented Feb. 20, 1951 UNITED STATES PATENT OFFICE RESETTING CURRENT TRIP MECHANISM John G. M. Viti, Philadelphia, and John L. Lappin, Drexel Hill, Pa.., assignors to General Electric Company, a corporation of New York Application January 10, 1948, Serial No. 1,547

4 Claims. 1

This invention relates to operating mechanisms for electric circuit breakers and, more particularly, to a device intimately associated with the latching mechanism and the main operating crank of a circuit breaker of the biased open type for the purpose of tripping the circuit breaker open upon predetermined conditions.

Tripping mechanisms such as that disclosed in United States Patent 2,247,861, Thumin et al., assigned to the assignee of the present invention, are constructed as a separate unit and are adapted to be attached to the circuit breaker operating mechanism as a supplementary tripping means responsive to smaller current impulses than those required to operate the main tripping mechanism.

Because a considerable number of circuit breaker applications will of necessity require a sensitive current responsive tripping mechanism and because certain advantages will result if the sensitive tripping mechanism is constructed as an integral part of operating mechanisms of the type disclosed in the above mentioned Patent 2,247,861 Thumin et al., our invention is adapted to form an integral part of the operating mechanism for circuit breakers requiring sensitive current responsive tripping means.

A principal object of our invention is the provision of an improved automatically operable tripping device and resetting mechanism therefor for an electric circuit breaker, wherein the tripping mechanism is automatically reset after a tripping operation, in accordance with the opening movement of the circuit breaker.

Another object of our invention is the provision of a tripping device which is mounted on the same shaft as the circuit breaker latching member and which is automatically conditioned for a subsequent tripping operation by means operated by the opening movement of the main operating crank of the circuit breaker Still another object of our invention is the provision of an operating mechanism incorporating our improved tripping device which is capable of trip free closing during the latter part of the circuit breaker closing operation.

A still further object of our invention is to provide a tripping device with a novel resetting arrangement wherein the resetting member picks up the tripping impact member at an instant when both members are relatively stationary thereby avoiding destructive shocks to the tripping mechanism Y Our invention will be more fully set forth in the following description referring to the accom- 2 panying drawing, and the features of novelty which characterize our invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

Referring to the drawing, Fig. l is an elevational view, partly in section, of an electric circuit breaker employing the tripping mechanism of our invention; Fig. 2 is an enlarged'view of a portion of Fig. 1 illustrating the tripping mechanism when the circuit breaker is in the closed position; Fig. 3 is a view similar to Fig. 2 showing the tripping mechanism an instant before the circuit breaker is tripped; and Fig. 4 is a view similar to Figs. 2 and 3 showing the tripping mechanism just after the completion of an opening operation of the circuit breaker.

Although the operating mechanism of our invention is applicable to various types of electric circuit breakers and switches, we have chosen to illustrate the invention specifically as applied to circuit breakers of the type disclosed in Linde Patents 2,293,513 and 2,335,068 granted August 18, 1942, and November 23, 1943, respectively, and assigned to the same assignee as the present application. This circuit breaker is generally indicated in Fig. 1 by the numeral I and comprises a pair of relatively movable contacts 2 and 3. The contact 3 is a movable, contact and is sup" ported on an arm 4 rotatable about a pivot 5. The operating mechanism is mounted in a housing 6 closely associated with the housing I of the circuit breaker I. A suitable insulating link 8 interconnects pivotally mounted arm 4 with the operating mechanism generally indicated at 9.

The motive means for operating mechanisms for electric circuit breakers, as will be understood by those skilled in the art, might be a fluid m0- tor, electric motor, solenoid, or any suitable means. For the purpose of illustrating our invention, the motive means of the operating mechanism 9 is illustrated as a solenoid l0 and a vertically movable armature H attached to an operating plunger l2. Solenoid I0, as illustrated in the drawings, is mounted beneath the operating mechanism linkage and is supported between a pair of parallel side walls, only one of which appears in the drawing as the side wall I3, which together with its corresponding wall form in efiect a housing for the operating linkage and the parts of our invention associated therewith. Preferably, the solenoid I0 is supported from side wall I3 and the corresponding side wall or, if desired, the solenoid I0 may be supported by a base plate l4. Base plate It is provided with an opening l5 through which plunger l2 may extend. The thrust transmitting linkage of the operating mechanism comprises the operating or out-put crank 16, pivotally mounted at ll between plate i3 and its cooperating plate which is not shown. One end of main operating crank I6 is pivotally connected as at l8 to the link 8. The other end of operating crank 16 is curved and is connected by pivotal means as indicated at 9 to a collapsible or floating linkage generally indicated at 26. This linkage 20 is very similar to that disclosed and claimed in Thumin Patent 1,627,526 granted October 13, 1931, and assigned to same assignee as the present application.

Floating or collapsible linkage 20 comprises link 2i and the link 22 pivotally related by a shaft having an extension 23. A suitable icated at with a U-shaped crank 26 roatable about a fixed pivot 21 supported between ate l3 and its corresponding plate which is not shown. It will be observed from the drawings that the links 2i and 22 form a toggle with the shaft having the extension 23 as the knee joint thereof. The plunger l2 is adapted in its upward movement to engage the roller 24 positinned at the knee of the toggle and upward movement thereof straightens the thrust-transmitting toggle comprisin the links 2! and 22 thereby causing rotation of operating crank IS in a clockwise direction about the pivot 11 for actuating the circuit breaker to its closed position.

Rotatable about pivot 25 (between the link 22 and crank or lever 26) is a trip latch roller 28 which is adapted either to rest on a stop bolt 29 supported from the plate [4, the proper height of which may be adjusted in a manner which is obvious from the drawing, or alternatively, to be urged against the arcuate latching face of the trip latch 3| as shown in Figs. 2 or 3. A suitable resetting spring 30 for the thrust linkage tends to rotate lever 26 in a clockwise direction so that, with the mechanism open and the links reset as shown dotted in Fig. 4, the ip latch roller 28 rests upon stop bolt 29. It

will be obvious from a study of the drawing that if trip latch roller 28 is maintained in a ilxed position between stop bolt 29 and the latch 3|, an upward force applied to toggle roller 24 will cause rotation of operating crank l5 about pivot l1. move away from stop bolt 28 at any instant after the upward movement of the plunger 12 has commenced, then the thrust transmitting linkage collapses toward the left and the clockwise closing rotation of operating crank I6 is permitted to reverse because roller 24 now can ride to the left oil the plunger l2 due to the crank 26 rotating counterclockwise against the bias of its resetting spring 30. In order to instantaneously release the trip latch roller 28 from its normally held position close to stop bolt 29, thereby to render the mechanism mechanically trip-free, there is provided the trip latch 3| pivotally mounted at 32 to side plate l3 and its cooperating side plate which is not shown. A resettin spring 12 is provided for returning the latch 3| to its normal holding position as shown in Fig. 2 after being tripped and then driven by roller 28 to its approximate extreme position of rotation as shown in Fig. 4.

If, however, trip latch roller 28 is freed to The opening bias for the circuit breaker is supplied by a main spring 33 mounted on vertically slidable guide rod 34 between plate 35 and yoke 36. Yoke 36 is pivotally mounted at 31 to side plate [3 and its cooperating side plate which is not shown.

In order to restrain the collapsible linkage 20 in the thrust transmitting breaker closed position indicated in Figs. 1 to 3, a pivotally mounted prop 38 is provided. Prop 38 is rotatable about a shaft 39 supported between side plate [3 and its cooperating side plate which is not shown in the drawings. A suitable resetting spring 40 biases prop 3B in a counterclockwise direction against a stop 4|. When collapsible linkage 2D"is moved to the position indicated in Figs. 1 to 3 by upward movement of plunger l2, prop 38 moves under the extension 23 of the shaft forming the knee of the toggle comprising the links 21 and 22 for supporting the linkage in the breaker closed position alter plunger l2 drops to its lowermost position coincident with the dcenergizing of the closin coil 10 and as indicated in all of the figures.

For tripping the breaker open by causing the linkage 20 to collapse, it is necemary to force the latch 31 out of restraining engagement with roller 28 in a clockwise direction about its supporting shaft 32. In accordance with our invention, an impact member 45 which is rotatably mounted on shaft 32 is provided. The impact member 45 is constructed of a pair of plate members which straddle the latch CH. The two plate membes are joined together by a welded or integrally constructed bridging portion 46 shown in section in all of the drawings. Impact member 45 is biased for rotation in the clockwise direction by a sprin 41 which is mounted on a guide rod member 48 between a fixed plate 49 and a yoke member 50. Rod 48 has an extension 5| which is slidably mounted in a diametral opening in the pivotal guide pin 52. Pin 52 is journally supported for rotation in supporting member 53 which in turn is secured to supporting plate l3 and its corresponding supporting plate, not shown. Yoke is 1'0- tatable about a shaft 54 which is secured to the two plates of impact member 45. Impact member 45 is restrained in the position shown in Fig. 2 by rotatable trip shaft 55 which is constructed with a notched section 56. A radially extending rod 51 is secured to shaft 55 and is positioned to be engaged by a tripping pin 58 mounted on a trip plunger 59. Upward motion of plunger 59 may be achieved by any suitable means such as by solenoid 43. Solenoid 43 and plunger 59 are supported on a supportin plate 60 which may be secured to supporting plate I3 and its corresponding supporting plate which is not shown or which may form an integral part of supporting member 53. An adjusting means for determining the precise reset position of shaft 55 comprises a, radially extending rod 42 secured to shaft 55 and a cooperating adjustable stop 44 which mechanism functions in a manner which is obvious from Figs. 1 and 3.

In order to provide a cushioned sto for impact member 45 when such member is rotated counterclockwise to its reset position, a bumng means is provided comprising the compressible spring 61 mounted on plunger 52. The upper end of spring Bl bears against the head 63 of plunger 62 and the lower end of spring 5| bears against an apertured guide bracket 64 mounted on supporting member ll. Plunger 82 is limited When a predetermined current is supplied to solenoid 43 by any suitable means responsive to abnormal line or other conditions as is well understood in the art, upward tripping motion of plunger 59 is initiated. When pin 58 on rod 59 collides with rod on shaft 55, shaft 55 is caused to rotate in a clockwise direction. This rotation will be sufficient to cause the projection 51 on the two plates of impact member 45 to pass through the notch 56 on shaft 55 due to the action of compression spring 41. Connecting portion 46 of the impact member 45 will collide with latch 31 at such time as impact member 45 will have rotated in a clockwise direction to the position shown in Fig. 3. The force of the impact will cause latching member 3| to rotate against the bias of spring 12 in a clockwise direction about its shaft 32 and latch roller 28 will be iree to rotate to the left about its pivot 21 thus causing a collapse of the linkage 20 to the position shown by solid lines in Fig. 4, and resulting in the opening of the circuit breaker I. Shortly after the circuit breaker I is opened the linkage 20 and associated parts will be moved to the position shown by dotted lines in Fig. 4 by spring 30.

If the above described tripping operation occurs when the breaker is fully closed as shown in Fig. 2, it will be understood that the toggle knee pin 23 rides to the left from off the holdclose supporting prop 38. If, however, tripping is initiated before the closing stroke is completed, it will be appreciated that a similar linkage collapsing action occurs excepting that in such case the toggle knee roller 24 rolls to the left from off the end of the ascending plunger l2.

In order to condition the tripping device for the next closing operation, there is provided a suitable resetting member 68 which is pivotally connected at its right hand end by a projection 59 on link 68 to the main operating crank ii of the circuit breaker I. In the embodiment shown, this resetting member 68 conveniently takes the form of a connecting rod or link, suitably curved for avoiding interference with the pin 23. Reset rod or link 68 is connected at its left hand end to one of the plates of the impact member 45 by a projection portion of reset rod or link 58 and which projection is slidable in the lostmotion slot H in one of the side plates compris-- ing the impact member 45. It will be observed that the projection 68 of reset link or rod 58 1S pivoted to operating crank It at a point slightly above the level of the pivot I! when the breaker is closed as shown in Figs. 1-3. Thus, after the latch 3| has been tripped and as the circuit breaker begins to move toward its open position the pivotal connection 69 will first move downwardly with negligible lateral displacement produced in the reset rod 68 before moving to the right due to the arcuate path of pivot 69 about fixed pivot II. The tripping energy imparted to impact member 45 by spring 41 is transferred through impact to the trip latch 3| so that the speed thereof is substantially checked before link 58 begins moving to the right coincident with opening movement of crank It to reverse the clockwise rotation of impact member 45 for performing a resetting operation thereof.

Fig. 3 best shows this feature of our invention, for at the instant shown, the impact member's bridgepiece 46 is colliding with the trip latch II and is about to impart energy and motion to the latter so that it will rotate to release the linkage. It will be noted that the righthand end of the lost-motion slot ll has not yet engaged the projection I0 of .the resetting rod 68 so that a small gap exists therebetween at this moment which provides for a slight followthrough movement for the impact member. So far, the impact member 45 has moved independently of the resetting member 68.

Because the rotation of the impact member 45 has been substantially arrested by its impacting the trip latch 3|, and because the reset rod has not yet been caused to move toward the right by the released output crank IS, the resetting rod 68 becomes operatively related to the impact member 45 (i. e. with projection in engaging the righthand end of slot II) at an instant when both of these members are substantially at rest. Furthermore, the pickup action for resetting the member 45 is achieved gradually, smoothly and with low relative velocity by virtue of the reset rods projection 69 rotating out from its dead center toggle relationship. Accordingly, the reset operation of our invention is performed with a smoothness and absence of shock hitherto impossible with prior methods for resetting a tripping device during the opening movement of a circuit breaker.

Just after the circuit breaker completes its opening stroke the mechanism will have assumed the position shown by solid lines in Fig. 4. From this illustration it will be observed that, to ensure positive resetting, the rod 68 has rotated the impact member 45 so as to provide a small clearance gap between its projecting tip 61 and the latching surface of trip shaft 55. This gap will be closed at the commencement of the next closing stroke to restore tripping control immediately to the latch 55 as illustrated in Fig. 2.

As the breaker is closed the link 68 is moved toward the left so that after closing the above mentioned gap, the projection 10 on link 68 now is moved to the left in slot H, i. e. independently of the impact member 45. Since the major displacement of link 68 to the left is accomplished during the initial portion of the closing movement of operating crank IS the impact member becomes free to trip soon after a closing operation has been initiated or substantially before such operation has been completed. Thus, the circuit breaker mechanism is mechanically tripfree during the major portion of the closing operation of main operating crank Hi.

It should be understood that our invention is not limited to the specific details of construction and arrangement thereof herein illustrated, and that changes and modifications may occur to one skilled in the art without departing from the spirit of our invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. An operating mechanism for an electric circuit breaker comprising a main rotatable operating crank, a linkage mechanism for operating said crank, a shaft, a latch rotatably mounted on said shaft and effective to hold said linkage in the closed position by engagement therewith, a spring biased rotatable impact member mounted on said shaft and operable to trip said latch out of holding engagement with said linkage, means for holding said impact member in a position out of engagement with said latch and for releasing said impact member for rotation under the force of its biasing spring, a, resetting member connected for movement in accordance with the operating stroke of said crank, said resetting memher being disposed with respect to the center of rotation of said crank so that substantially no resetting movement of said resetting member occurs during the initial opening movement of said crank and said resetting member being operably related to said impact member to produce a pickup action upon said impact member subsequent to the tripping movement thereof, the tripping movement of said impact member being substantially arrested after tripping of said latch.

2. An automatically operable tripping and resetting mechanism for an electric circuit breaker of the biased open type comprising a pivotally mounted operating arm having an open and closed position, means including a latching member for holding said arm in the closed position under predetermined conditions, an impact member having a normal position and being spring biased toward an operated position to trip said latching member under predetermined conditions, means for engaging said impact member and operable to release said impact member to allow movement thereof to its operated position under predetermined conditions, the tripping movement of said impact member being substantialy arrested after tripping of said latching member, and a reset rod connected between said impact member and said operating arm and movable in accordance with movement of said arm and occupying an approximate dead center position with respect to said operating arm when said arm is in the closed position so that said rod is gradually accelerated as said operating arm rotates about its pivot toward its open position to cause a low velocity pick-up of said impact member thereby to return said impact member to its normal position in order to reset said impact member without shock.

3. An automatically operable tripping and resetting mechanism for an electric circuit breaker of the biased open type comprising a pivotally mounted operating arm having an open and a closed position, a fixed shaft, a means including a latching member mounted on said shaft for holding said arm in the closed position under predetermined conditions, an impact member mounted on said shaft and rotatable thereon to trip said latching member, means for engaging said impact member and operable to release said impact member under predetermined conditions, the tripping energy of said impact member being substantially absorbed by said latching member,

and a reset rod movable with said arm and connected to said impact member by a lost motion connection and occupying an approximate dead cented position with respect to said am when said arm is in the closed position so as to effect a low velocity pick-up of said impact member, said reset rod occupying an over-center position with respect to said operating arm when said arm is in the open position so as to allow substantial relative movement between said rod and said impact member during the initial part of the movement of said arm toward its closed position.

4. An automatically operable tripping and resetting mechanism for an electric circuit breaker, comprising a latching member, an impact member operably related with said latching member and capable of tripping said latching member under predetermined conditions, means for engaging said impact member and operable to release said impact member under predetermined conditions, the tripping energy of said impact member being substantially absorbed by said latching member, an operating arm having an open and a closed position, and means for resetting said impact member comprising a connecting link movable in accordance with movement of said arm, said lirl and said arm being in an approximate dead center toggle relationship with one another when said arm is in the closed position for producing a smooth relatively low velocity pick-up action upon said impact member when said arm is moved toward its open position.

JOHN G. M. VI'II. JOHN L. LAPPIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 707,952 Benzinger Aug. 26, 1902 1,915,951 Pinkham June 27, 1933 1,953,789 Thumim Apr. 3, 1934 1,956,847 Ainsworth May 1, 1934 2,053,961 Linde Sept. 8, 1936 2,140,371 Ow et al Dec. 13, 1938 2,246,298 Dyer June 17, 1941 2,247,861 Thumim et a1. July 1, 1941 2,247,862 Thumim July 1, 1941 2,274,350 Thumim Feb. 24, 1942 2,436,194 Bush Feb. 17, 1948 

